1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹

Here's why:

* Normal Configuration: You might expect copper (Cu, atomic number 29) to have the configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁹ 4s².

* Exception: However, copper deviates from this expected configuration due to the stability of a completely filled d-orbital. Moving one electron from the 4s orbital to the 3d orbital results in a more stable configuration with a full 3d shell (3d¹⁰).

* Stability: This slight energy difference, where a full d-orbital is more stable, causes the unusual configuration of copper.

Therefore, the final configuration of copper is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹.